Apparatus for placing power control data in a transmission signal

ABSTRACT

A device for placing power control data in a transmission signal has: a generating device for generating power control data as a function of a received signal, a buffer for buffering a formatted transmission data word that contains a power control data field for recording power control data, an inserting device for inserting the generated power control data into the power control data field of the buffered transmission data word, and a modulation device for modulating the transmission data word to form a transmission signal with a transmission power corresponding to the power control data.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation of copending InternationalApplication No. PCT/DE99/03538, filed Nov. 4, 1999, which designated theUnited States and was not published in English.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to an apparatus for placing power controldata in a transmission signal, in particular in the form of a CDMA (CodeDivision Multiple Access) transmission signal.

[0004] In mobile radio systems, mobile radio stations MS communicatewith a base station BS. Since the number of the mobile stationssimultaneously communicating with a base station is high, thetransmission power of a transmission signal must be controlled both inthe case of the mobile station MS and in the case of the base station BSso that transmission signals of different stations do not interfere withone another. CDMA (Code Division Multiple Access) is a channel accessmethod that is used in cellular mobile radio systems. In CDMA mobileradio systems, a plurality of subscribers, which differ from one anotheronly by an orthogonal subscriber-specific spread signal code applied tothe transmission signal, transmit simultaneously in the same frequencyband. A separation of the different subscribers is achieved bybackspreading by using the respective subscriber-specific orthogonalcode. However, received signals are no longer completely orthogonalbecause of the real mobile radio channel. In order to permit separationof the signals, it is therefore necessary for the various receivedsignals to arrive at the receiver with approximately the sametransmission power, since otherwise the desired signals are so stronglydisturbed by interference with the transmission signals of othersubscribers that separation is no longer possible.

[0005] CDMA mobile radio systems therefore require a particularly fastpower control of the transmission signal both in the mobile radiostation MS and in the base station BS.

[0006] The power control of the respective transmitter of a station isperformed by power control data that are obtained from the receivedsignal of that station with which the relevant station is communicating.The power of the transmission signal of the base station BS for aspecific subscriber is controlled via a power control signal TPC of themobile station MS. Conversely, the power of the transmission signal ofthe mobile station MS is controlled by the power control signal TPCtransmitted by the base station BS. The generation of the respectivecontrol data in a station is performed in this case by evaluating thetotal signal received by the station by means of asignal-to-interference plus noise ratio estimate, that is to say what istermed an SINR estimate.

[0007]FIG. 1 shows a prior art apparatus for inserting power controldata.

[0008] The transmission data to be transmitted by the station are fed toa coder and multiplexer 40. The coded and multiplexed transmission dataare formatted in a formatter into a transmission data word with aplurality of data fields. The transmission data word in this case has alength of one time slot of the mobile radio system. The data fieldsserve to record information data, pilot data, formatting data and powercontrol data TPC.

[0009] The power control data TPC are obtained in a control datagenerating device 44 by an SINR estimation of a received signal that hasbeen conditioned by a received signal conditioning circuit 46. All datathat are to be transmitted within a time slot of the mobile radiosystem, such as information data, pilot data, formatting data and thepower control data TPC, are put together in the formatter 42. Theformatting is undertaken, for example, in a DSP processor ormicrocontroller. The finally formatted transmission data word istransmitted via a signal interoffice trunk, for example a BUS, into aninput buffer 48 of a modulator 50. The input buffer 48 usually has amemory capacity that corresponds to the data length of two time slots ortwo transmission data words. The modulator 50 conditions thetransmission data word stored in the input buffer 48 for signaltransmission. For this purpose, it uses orthogonal OVSF codes that arestored in a memory 52 to carry out spreading in a CDMA mobile radiosystem. Furthermore, encryption or scrambling is performed withencryption codes that are generated by an encryption generator V. Thetransmission signal is subsequently generated by digital-to-analogconversion by a downstream D/A converter 54.

[0010] As may be seen from FIG. 1, a delay time interval thatcorresponds to the memory capacity of the buffer 48 exists between theinstant at which the power control data TPC are generated for control onthe basis of an interference plus noise ratio estimate, and the instantat which the power control data TPC are conditioned by the moderator 50for transmission. Particularly in the case of CDMA mobile radio systemsthat require a particularly fast power control, such a long reactiontime until the power control data TPC are transmitted after the SINRevaluation can lead to a substantial worsening of the signaltransmission because of interference with transmission signals fromother subscribers.

[0011] Published European Patent application EP 0 893 889 A2 discloses amethod and an apparatus for controlling the transmission power in a CDMAcommunications system. On the basis of an SINR estimate, a TPC signal isgenerated and fed to what is termed a level controller, which generatespower control data that are then inserted by what is termed the timemultiplexer into the power control data field of the bufferedtransmission data word. The apparatus also has a modulation device formodulating the transmission data word to form a transmission signal witha transmission power corresponding to the power control data.

SUMMARY OF THE INVENTION

[0012] It is accordingly an object of the invention to provide anapparatus for placing power control data in a transmission signal whichovercomes the above-mentioned disadvantages of the prior art apparatusof this general type.

[0013] In particular, it is an object of the invention to provide anapparatus for placing power control data in a transmission signal suchthat the transmission power of the station can be quickly controlled.

[0014] With the foregoing and other objects in view there is provided,in accordance with the invention, an apparatus for placing power controldata in a transmission signal. The apparatus includes: a generatingdevice for generating power control data as a function of a receivedsignal, a buffer for buffering a formatted transmission data word thatcontains a power control data field for recording power control data, aninserting device for inserting the generated power control data into thepower control data field of the buffered transmission data word, and amodulation device for modulating the transmission data word to form atransmission signal whose transmission power is controlled by the powercontrol data.

[0015] In accordance with an added feature of the invention, thetransmission signal is a CDMA transmission signal.

[0016] The generating device for generating transmission power controldata generates the transmission power control data preferably using asignal-to-interference plus noise ratio estimate of the received signal.

[0017] In accordance with an additional feature of the invention, theformatting device formats coded and multiplexed transmission data into aformatted transmission data word.

[0018] The formatted transmission data word preferably consists of aplurality of data fields.

[0019] The length of the formatted transmission data word is preferablyidentical to the length of the CDMA time slot.

[0020] The power control data field of the formatted transmission dataword is filled with predetermined filler data in the formatter in apreferred embodiment.

[0021] The filler data are preferably designed such that they effect nochange in the transmission power.

[0022] The formatting device is preferably connected to the buffer via asignal bus.

[0023] In accordance with another feature of the invention, themodulation device is a digital modulator, and a digital-to-analogconverter is connected downstream of the digital modulator.

[0024] Other features which are considered as characteristic for theinvention are set forth in the appended claims.

[0025] Although the invention is illustrated and described herein asembodied in a apparatus for placing power control data in a transmissionsignal, it is nevertheless not intended to be limited to the detailsshown, since various modifications and structural changes may be madetherein without departing from the spirit of the invention and withinthe scope and range of equivalents of the claims.

[0026] The construction and method of operation of the invention,however, together with additional objects and advantages thereof will bebest understood from the following description of specific embodimentswhen read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 shows a prior art apparatus for inserting power controldata; and

[0028]FIG. 2 shows an inventive apparatus for implementing power controldata in the form of a transmission signal.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Referring to FIG. 2, it can be seen that the transmission data tobe transmitted by the station pass, via a transmission data input 1 ofthe inventive power controller and a data line 2, to a coding andmultiplexing device 3. The coded transmitted data are fed via aninternal line 4 to a formatting device 5. The formatting device 5formats the coded transmission data into formatted transmission datawords. The formatted transmission data words respectively include aplurality of data fields that contain information data, pilot data, andformatting data. Moreover, the transmission data words respectively havea power control data field that is reserved for recording power controldata. The power control data field of the formatted transmission dataword is filled with filler data, for example, a sequence of binary zerosobtained via a line 6. The filler data are such that they cause nochange in the transmission power. The formatting device 5 outputs theformatted transmission data words to an input buffer 8 of the modulator9, via signal interoffice trunks 7 that form a signal bus, for example.

[0030] The buffer 8 is connected to a data inserting device 100 thatreceives power control data via a control line 10 from a generatingdevice 11 for generating power control data. The generating device 11for generating power control data preferably generates the power controldata using a signal to interference plus noise ratio estimation or SINRestimation from a received signal that has been conditioned by areceived signal conditioning circuit 12. The received signal received bythe station is fed via a line 13 to the received signal conditioningcircuit 12 and is conditioned there as a signal. The received signalconditioning circuit 12 contains a plurality of stages such as filters,analog-to-digital converters, pulse shapers RRC, rake circuits and anMRC circuit (Maximum Ratio Combining). The output of the signalconditioning circuit 12 is connected, via a line 14, to the generatingdevice 11 for generating the power control data.

[0031] The power control data generated in the generating device 11 arewritten, via line 10 and the insertion device 100, directly into thepower control data field of the transmission data word located in thebuffer 8. The filler data are overwritten in the process. Thetransmission data word completed by the writing in of the power controldata passes, via a line 15, to the actual modulation device 16 of themodulator 9. The modulation device 16 modulates the transmission dataword. The spreading of the narrow band signal into a broadband signal isperformed using an orthogonal OVSF code. The OVSF code is stored in abuffer 17 and is fed to the modulation device 16 via a line 18.Furthermore, the modulation device 16 receives an encryption orscrambling code for encrypting the transmission signal. The scramblingcode is generated by a generator 20. The transmission signal modulatedby the modulation device 16 is output, via a line 21, to adigital-to-analog converter 22 that generates an analog transmissionsignal. The analog transmission signal is output to a transmissionantenna via a line 23.

[0032] The power control data pass directly into the modulator 9 withoutdelay because of the fact that the power control data that are generatedby the generating device 11 are written directly into the buffer 8 ofthe modulator 9. The reaction time of the power control, as it is shownin FIG. 2, with regard to changes in the received signal power of thesignal received via the line 13 is thereby substantially shortened. Thisentails an improvement in the system performance. Power fluctuations inthe received signal received from a different station are detected in avery short time by the power controller inside the relevant station, sothat the latter can amplify or attenuate its own transmission signalcorrespondingly. The power control data or power control informationdata are thus transmitted substantially quicker in the case of the powerregulation according to the invention. In this case, the input buffer 8already present in the modulator 9 can be utilized to insert the powercontrol data TPC.

We claim:
 1. An apparatus for placing power control data in atransmission signal, comprising: a formatting device for formattingcoded transmission data into a formatted transmission data word having apower control data field for recording power control data, saidformatting device filling the power control data field of the formattedtransmission data word with predetermined filler data causing no changein a transmission power; a generating device for generating powercontrol data as a function of a received signal; a buffer for bufferingthe formatted transmission data word; an inserting device foroverwriting the filler data in the power control data field of theformatted transmission data word in said buffer by inserting the powercontrol data from said generating device into the power control datafield of the formatted transmission data word in said buffer; and amodulation device for modulating the formatted transmission data word toform a transmission signal with a transmission power corresponding tothe power control data.
 2. The apparatus according to claim 1, whereinthe transmission signal is a CDMA transmission signal.
 3. The apparatusaccording to claim 2, wherein said generating device generates the powercontrol data from the received signal using a signal-to-interferenceplus noise ratio estimate SINR.
 4. The apparatus according to claim 1,wherein said generating device generates the power control data from thereceived signal using a signal-to-interference plus noise ratio estimateSINR.
 5. The apparatus according to claim 1, wherein the formattedtransmission data word includes a plurality of data fields.
 6. Theapparatus according to claim 1, wherein the formatted transmission dataword h as a length of a CDMA time slot.
 7. The apparatus according toclaim 1, comprising: a signal bus connecting said formatting device tosaid buffer.
 8. The apparatus according to claim 1, wherein saidmodulation device is a digital modulator.
 9. The apparatus according toclaim 1, comprising: a digital-to-analog converter connected downstreamfrom said modulation device.